Abstract
To date land based aquaculture systems such as Recirculating Aquaculture Systems (RAS) have to regulate and control the release of excess water (usually rich in Nitrogen (N)). The release of N-rich water in the environment can lead to undesirable eutrophication, and regulations, to avoid and control this, are increasing. Water treatment before release is mandatory and implies a cost to the producer. At present, there is no established system for collection and reuse of RAS release water into new productions. The release from post-smolt RAS is saline and favours production of organisms that tolerate brackish or seawater such as seaweeds or marine microorganisms. In the project WASTELESS we introduce secondary water treatment in RAS by testing the integration of a photo bioreactor (PBR) module. In this module, organisms naturally growing on RAS water will bio-remediate the water and the produced biomass will be investigated for use in fish feed. The area footprint of the reactor treating the effluent from RAS can be minimized by increasing the height and length of the belt, and harvesting of a biofilm is energy efficient compared to harvesting by centrifugation. We aim at establishing multi-species biomass production and use known ecological principles to optimise nutrient removal and cleaning of the RAS water. We have run several experiments mimicking the growth of the natural biofilm present at RAS facility and will present sequencing results indicating the prokaryotic and eukaryotic genera and/or species that dominate the biofilm together with a biochemical profile of the biomass (proteins, lipids). Potentially new ingredients for aquafeed can be produced from the N-rich RAS release by biorefining the produced biomass paste into clean fractions of proteins and fatty acids for example to replace less sustainable ingredients in aquafeed such as soy or fish oil.